Synthesis And Characterization Of Dopamine-Modified Sulfonated Poly(Arylene Ether Sulfone) For Proton Exchange Membrane

Proton exchange membrane fuel cell?PEMFC?can directly convert the chemical energy of fuel into electrical energy without the Carnot cycle and it has the advantages of high efficiency,long life,no pollution to the environment and a wide range of fuel sources.The proton exchange membrane is the core part of the fuel cell and plays the role of separating fuels and transferring protons.The currently commercially representative membranes are perfluorosulfonic acid membranes,such as Nafion made by DuPont.The main disadvantages of this material are high cost,not easily degraded waste,serious environmental pollution and the complicated manufacturing process,which limit its wide application in fuel cells.Sulfonated poly?arylene ether sulfone??SPAES?has advantages such as good mechanical properties,thermal stability,easy synthesis,low cost,easily degradation and zero emission of pollutants.However,the proton exchange membrane is greatly affected by the degree of sulfonation?DS?.Proton conductivity will not meet the requirements of proton exchange membrane fuel cell at the low DS,while the high DS may cause the loss of the mechanical properties of the membrane,thereby reducing the service life of the fuel cell.In order to overcome the drawbacks of sulfonated poly?arylene ether sulfone?,this dissertation mainly focuses on the fabrication of dopamine-modified sulfonated poly?arylene ether sulfone?for proton exchange membrane?PEM?and the effection of the highly crosslinked structures and basic groups of polydopamine to the PEM properties.Dopamine-grafted sulfonated poly?arylene ether sulfone?crosslinking membrane,dopamine modified sulfonated poly?arylene ether sulfone?--sulfonated POSS hybrid membrane and sulfonated poly?arylene ether sulfone?--dopamine modified sulfonated POSS hybrid membrane were prepared and the effect of self-polymerization of modified dopamine on the properties of sulfonated poly?arylene ether sulfone?was investigated.The details are as follows:1.Dopamine is grafted to the side chain of the sulfonated poly?arylene ether sulfone?,and then dopamine-grafted sulfonated poly?arylene ether sulfone?was crosslinked using dopamine self-polymerization technique.The results show that the sulphonated poly?aryl ether sulfone?membranes modified by covalent bond and cross-linking structure had significantly lower swelling ratio and methanol permeability,and exhibited the stability of the material.2.A series of dopamine modified sulfonated poly?arylene ether sulfone?-sulfonated POSS hybrid membrane?SPAES/sPOSS/D?were prepared.Compared with plain SPAES/sPOSS hybrid membranes,while maintaining high proton conductivity,the dopamine modified membranes demonstrated lower membrane swelling and better dimensional stability.The polydopamine layer inhibits the attack of free radicals to polymer backbone,therefor the hybrid membrane was not completely degraded in Fenton reagent for 12 hours,and exhibited good oxidation stability.3.Aiming at the defects that a large amount of sulfonic acid groups in the additive POSS result in poor stability of the oxidation resistance of the membrane and a decrease in mechanical properties,sulfonated poly?arylene ether sulfone?-dopamine modified sulfonated POSS hybrid membrane?SPAES/D-sPOSS?were prepared.The acid-base interactions of dopamine-modified sPOSS and the sulfonic acid groups of the main chain of the polymer,enhanced the internal compactnes of the membrane and providing excellent comprehensive performance as PEM.The hybrid membrane of SPAES/D-sPOSS-2 showed good mechanical properties in the dry state.Young's modulus was 1.48 GPa,tensile strength was 50.82 MPa,and elongation was 7.25%.In addition to enhancing the dimensional stability and mechanical properties of the membrane and reducing the swelling rate,additional proton transmission channels are improved the proton conductivity of SPAES/D-sPOSS-2 hybrid membrane can as high as 0.242 S cm^-1 under 80 ^oC completely hydrated conditions,which is clearly superior to the commercial Nafion membranes(0.122 S cm^-1)and sulfonated poly?arylene ether sulfone?-sulfonated POSS hybrid membranes(0.163 S cm^-1).